[cfe-dev] How to use Clang to translate from C++ to another language

[Tim Stowell]

Thanks everyone for the responses, sounds like my best bet is to subclass
RecursiveASTVisitor. I'm curious, sounds like Clang worked well to
translate Objective-C to Javascript, since Javascript is similar to
Actionscript, any gotchas to look out for? Yes I agree multiple inheritance
would be a nightmare, I'm going to cheat by only converting C++ code that
doesn't use it.

On Wed, Mar 28, 2012 at 9:21 AM, Douglas Gregor <dgregor at apple.com> wrote:

>
> On Mar 28, 2012, at 3:26 AM, David Chisnall wrote:
>
> > On 28 Mar 2012, at 03:37, Tim Stowell wrote:
> >
> >> I've recently compiled Clang and LLVM on Windows. My goal is to use it
> to translate from C++ to another language (specifically Actionscript), but
> I'm not sure the best way to go about this. For example, if I invoke clang
> with the -ast-print "pretty print" option, it looks like Clang can get a
> faithful representation of the original code from its internal AST. Do I
> need to somehow mimic that code so I get a pretty print in my new language?
> Or should I walk the AST tree? Thanks for any help!
> >
> > Yes, that's likely to be the best approach - it's what I did to
> translate Objective-C to JavaScript.  You will probably want to create a
> clang plugin that subclasses RecursiveASTVisitor.  This should walk the AST
> and emit code for your target language.
> >
> > You could use the rewriter, but I would strongly recommend against it.
>  For example, when translating a class with multiple inheritance into
> ActionScript you will need to create a class that composes them and then
> turn pointer casts into some fairly complex logic for accessing the
> relevant class (upcasts, in particular, are going to be especially horrible
> - no idea how you plan on implementing these) so trying to do simple
> rewriting is going to involve a lot more pain than simply writing out a new
> program from the AST.
>
>
> Right. The rewriter is good when you're just changing from one dialect to
> another within the same base language---Objective-C to C, C99 to C90,
> etc.---and want to preserve comments and code structure for all of the
> common parts. If the two languages are very different (C++ to
> Actionscript), you should either be transforming IR or walking the AST.
>
>        - Doug
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20120328/a02b7de9/attachment.html>